An ally is read as support arriving where it is needed, and as the parts of your life that stand with you. Dream books ask who the ally was, because that is where strength is being offered.
When this appeared in your dream, what were you feeling?
My Cosmic Code has a private dream journal. Write a dream down and the app picks out the symbols in it, shows what dream books say about them and, over time, which words recur across your entries. The journal is stored on your device only.